On June 1, we received "Implementation of necessary measures on fire 
prevention in relation to overhang-type high-voltage breakers at nuclear 
power stations (instruction)" * from Nuclear and Industrial Safety Agency 
(NISA), Ministry of Economy, Trade and Industry. 
                                      (Already announced on June 1st, 2011)

After that, following the instruction, we had confirmed the installation of
overhang-type high-voltage breakers in our nuclear power stations and put 
together the implementation plan on fire prevention measures as to the 
installation and reported to NISA today. 
                                                                        END

○ Attachment
Implementation of necessary measures on fire prevention in relation to
overhang-type high-voltage breakers at nuclear power stations (Report)
                                                                (PDF 161KB)

*Implementation of necessary measures on fire prevention in relation to 
 overhang-type high-voltage circuit breakers at nuclear power stations 
 (direction)
                                                   (May 30, 2011 NISA No.2)

On May 30, 2011, Nuclear and Industrial Safety Agency (hereinafter referred
to as "NISA") received a report from Tohoku Electric Power Co., Inc. on the
status of Onagawa NPS following the 2011 off the Pacific Coast of Tohoku 
Earthquake and the ensuing tsunami. 
According to this report, a fire broke out on the high voltage normal 
distribution panel at Unit 1 of the aforementioned NPS on March 11. The 
fire is understood to have been triggered when seismic motion caused an 
overhang-type high-voltage breaker of the distribution panel to swing, 
bringing the bonding conductor into contact with the surrounding structure 
and creating a short or a ground, which in turn caused an arc discharge 
with heat sufficient to touch off a fire. Based on this report and in order
to prevent similar fire incidents, NISA issued a written direction (see 
appendix) today, May 31, to commercial power reactor licensees to verify 
the presence if any of overhang-type high-voltage breakers at NPSs owned by
these licensees, and should such a breaker be present, draft an 
implementation plan for necessary measures for fire prevention such as 
upgrading to a high-voltage breaker with highly seismically-resistant 
design or installing a seismic trestle on the lower part of the 
overhang-type breaker, and report this to NISA by June 15 of this year.

Translation by NISA; 
http://www.nisa.meti.go.jp/english/press/2011/06/en20110610-3.pdf